Attach TransportFeedbackPacketLossTracker to ANA (PLR only)

webrtc/modules/congestion_controller/transport_feedback_adapter.cc

Index: webrtc/modules/congestion_controller/transport_feedback_adapter.cc
diff --git a/webrtc/modules/congestion_controller/transport_feedback_adapter.cc b/webrtc/modules/congestion_controller/transport_feedback_adapter.cc
index 87fab26c8af5c20f883cecc27e3bb17c97debc92..6900fcc1f8105091cf4174e4f5554f7c62c4c0f8 100644
--- a/webrtc/modules/congestion_controller/transport_feedback_adapter.cc
+++ b/webrtc/modules/congestion_controller/transport_feedback_adapter.cc
@@ -52,21 +52,34 @@ TransportFeedbackAdapter::TransportFeedbackAdapter(
       last_timestamp_us_(kNoTimestamp),
       bitrate_controller_(bitrate_controller) {}
 
-TransportFeedbackAdapter::~TransportFeedbackAdapter() {}
+TransportFeedbackAdapter::~TransportFeedbackAdapter() {
+  RTC_DCHECK(observers_.empty());
+}
 
 void TransportFeedbackAdapter::InitBwe() {
   rtc::CritScope cs(&bwe_lock_);
   delay_based_bwe_.reset(new DelayBasedBwe(clock_));
 }
 
-void TransportFeedbackAdapter::AddPacket(uint16_t sequence_number,
+void TransportFeedbackAdapter::AddPacket(uint32_t ssrc,
+                                         uint16_t sequence_number,
                                          size_t length,
                                          int probe_cluster_id) {
-  rtc::CritScope cs(&lock_);
-  if (send_side_bwe_with_overhead_) {
-    length += transport_overhead_bytes_per_packet_;
+  {
+    rtc::CritScope cs(&lock_);
+    if (send_side_bwe_with_overhead_) {
+      length += transport_overhead_bytes_per_packet_;
+    }
+    send_time_history_.AddAndRemoveOld(
+        sequence_number, length, probe_cluster_id);
+  }
+
+  {
+    rtc::CritScope cs(&observers_lock_);
+    for (auto observer : observers_) {
+      observer->OnPacketAdded(ssrc, sequence_number);
+    }
   }
-  send_time_history_.AddAndRemoveOld(sequence_number, length, probe_cluster_id);
 }
 
 void TransportFeedbackAdapter::OnSentPacket(uint16_t sequence_number,
@@ -96,6 +109,31 @@ int64_t TransportFeedbackAdapter::GetProbingIntervalMs() const {
   return delay_based_bwe_->GetProbingIntervalMs();
 }
 
+void TransportFeedbackAdapter::RegisterTransportFeedbackAdapterObserver(
+    TransportFeedbackAdapterObserver* observer) {
+  rtc::CritScope cs(&observers_lock_);
+  RTC_DCHECK(observer);
+  if (std::find(observers_.begin(),

[minyue-webrtc, 2017/02/22 11:47:55]

I would the sanity check be debug only:

RTC_DCHECK_NE(observers_.end(), observers_.find(...))

[elad.alon_webrtc.org, 2017/03/10 12:03:26]

Are you sure? Observer registration is not an often-occurring event, so the
inefficiency of searching through the handful of observers seems worth the extra
safety we get here. Wdyt?

[minyue-webrtc, 2017/03/17 09:20:31]

My points are:
1. no user actions seem to trigger RegisterTransportFeedbackAdapterObserver, so
runtime check may not be needed.
2. if you think there is really a need to take care of re-registration, we don't
need the else part.

[elad.alon_webrtc.org, 2017/03/17 10:10:32]

The else-clause is there to alert a programmer running freshly modified code
that breaks this assumption (just like the RTC_DCHECK you suggest).
I'll change the code according to your suggestion, although my personal
preference is for the extra check.

[minyue-webrtc, 2017/03/21 09:22:58]

As a reader's point of view, I would like to see that you either forbid it or
allow misuse. It is a bit confusing if we say "we forbid it, but in case you
forget ..." That's why for my suggested code.

+                observers_.end(),
+                observer) == observers_.end()) {
+    observers_.push_back(observer);
+  } else {
+    RTC_NOTREACHED();
+  }
+}
+
+void TransportFeedbackAdapter::DeRegisterTransportFeedbackAdapterObserver(
+    TransportFeedbackAdapterObserver* observer) {
+  rtc::CritScope cs(&observers_lock_);
+  RTC_DCHECK(observer);
+  auto elem = std::find(observers_.begin(), observers_.end(), observer);
+  if (elem != observers_.end()) {
+    observers_.erase(elem);
+  } else {
+    RTC_NOTREACHED();
+  }
+}
+
 std::vector<PacketInfo> TransportFeedbackAdapter::GetPacketFeedbackVector(
     const rtcp::TransportFeedback& feedback) {
   int64_t timestamp_us = feedback.GetBaseTimeUs();
@@ -156,6 +194,13 @@ void TransportFeedbackAdapter::OnTransportFeedback(
   }
   if (result.updated)
     bitrate_controller_->OnDelayBasedBweResult(result);
+
+  {
+    rtc::CritScope cs(&observers_lock_);
+    for (auto observer : observers_) {
+      observer->OnTransportFeedback(feedback);
+    }
+  }
 }
 
 std::vector<PacketInfo> TransportFeedbackAdapter::GetTransportFeedbackVector()